An apparatus for analyzing blood plasma, biological liquid or the like is already well-known, as disclosed in JP 10-501340 A (PCT), etc. In the “Modified Siphons for Improved Metering Precision” disclosed in the above-mentioned publication, the rotor of a centrifugal separator is equipped with a blood application chamber, a blood plasma measuring chamber, a retention chamber, a diluting agent measuring chamber, a mixing chamber, a measurement cuvette, etc.; in particular, the blood plasma measuring chamber and the mixing chamber communicate with each other through a siphon, wherein the positional relationship between the siphon inlet communicating with the blood plasma measuring chamber and the siphon outlet communicating with the mixing chamber is such that the inlet is situated outward of the outlet with respect to the radial direction of the rotor.
According to the invention disclosed in the PCT publication, when the rotor rotates, blood contained in the blood application chamber is moved by the centrifugal force to the blood plasma measuring chamber, where it is separated into cells and blood plasma. At the same time, the diluting agent contained in the retention chamber is moved by the centrifugal force to the diluting agent measuring chamber, and a portion of the diluting agent enters the mixing chamber from the diluting agent measuring chamber through a siphon.
The blood plasma separated from the cells in the blood plasma measuring chamber enters the mixing chamber through a siphon to be mixed with a diluting agent. The blood plasma that has been mixed with the diluting agent in the mixing chamber is distributed through a distribution ring to a large number of measurement cuvettes arranged in the circumferential direction of the rotor. Each of these measurement cuvettes, to which the diluted blood plasma is distributed, contains a reagent, which reacts with the blood plasma allowed to flow in and is finally subjected to photometric analysis.
The above-described invention disclosed in the above publication has a problem in that the measurement cuvettes subjected to photomeric analysis are previously provided with a reagent, which means only one kind of reagent is used for reaction with the diluted blood plasma.
Further, when the diluted blood plasma reacts with the reagent upon entering the measurement cuvettes containing the reagent, practically no agitating action is exerted, so that the reliability in the photometric analysis of the solutions in the measurement cuvettes is rather low.
The present invention has been made with a view toward solving the above problems in the prior art. It is an object of the present invention to provide a sample measuring device which allows a sample to successively react with one or more kinds of reagents, which reliably mixes and agitates the sample and the reagents prior to photometric analysis to thereby achieve high reliability in photometric analysis, and which is simple in construction and easily to handle.